Hi,
My lockes were doing just the same, 'bouncing' when I tried to lock it with the remote. After much advice taking I bought a used door lock motor from SW Vauxhall Spares (eBay) and fitted a drivers rear door one to my drivers door because it was the only one available, Needless to say it worked perfectly well and has never given problems since. Just make sure that you put the rods back in the exact positions they were removed and give the whole lot a good dose of light spray grease. If the rod for the interior lock rising button is even slightly bent it will cause your problem too. Hope you have very small hands, if not be prepareds to lose some skin. I did!
Your SatNav should be ok with a clean disk and you should also use a lens clearner. The standard DVD type is fine. Copied disks are not a problem if they are of good quality. I have copied my master disk as a backup, and used my copied one for years with no problems at all. The proof is in the pudding and can be seen working for those who state it cannot be done and will damage the laser!
Another possibility is that the unit may be damp inside or even something as silly as the eject button being nudged by something moving about in the boot.
Good luck m8t!